The present invention relates generally to metal refining, and more specifically, to consumable ingot electrodes therein.
Consumable ingot electrodes are used in various metallurgical processes for controlling metallurgical properties. For example, in vacuum arc remelting (VAR), a consumable electrode is lowered into a crucible maintained under vacuum for controlling the melting thereof. In electroslag remelting or refining (ESR), a consumable electrode is lowered into a crucible, which may have a gas environment, for electrical resistance heating and melting in a corresponding slag for refining the electrode material.
In both embodiments, it is desirable to measure the changing weight of the electrode as it is consumed for in turn controlling corresponding process parameters. This is typically accomplished by using a loadcell system which supports not only the electrode itself, but also the lowering mechanism attached thereto. Accordingly, the weight of the electrode itself is determined after subtracting extraneous loads measured by the loadcell corresponding with the various equipment attached to the electrode.
For example, portions of the lowering equipment are necessarily attached to the electrode and move therewith. This may include a hydraulic ram, or ball screw, or both. Various hoses may be also attached to the lowering mechanism for providing cooling water or inert gas. And, since the crucible typically defines a pressure vessel maintained under vacuum or under gas pressure, suitable seals must be provided between the lowering mechanism and the access port at the top of the crucible over which a substantial pressure difference is maintained. This pressure drop is variable during operation and introduces a variable additional force measured by the loadcell which must be removed in determining the actual weight of the electrode itself.
An improved form of electroslag refining is disclosed in U.S. Pat. No. 5,160,532-Benz et al in which a circumferentially segmented, cold induction guide (CIG) is disposed at the bottom of the electroslag crucible, and includes a drain orifice through which the refined melt may be drained for further use. For example, the melt may be discharged through a gas atomizer for spray forming the melt atop a suitable preform.
It is desirable to accurately control both the drain rate from the crucible for spray forming the preform, as well as controlling the melt rate of the electrode as it is consumed during the electroslag refining process. However, the typical loadcell weighing systems described above necessarily introduce extraneous measured loads in addition to the weight of the electrode itself which requires various corrections for isolating solely the electrode weight.
Accordingly, it is desired to provide an improved electrode weighing mechanism which reduces or eliminates extraneous loads in weighing the electrode.